Compensator for aircraft cable controls



Nov. 22, 1949 O. scHwlMMl-:R 2,489,163

ACOMI-"ENSATOR FOR AIRCRAFT CABLE CONTROLS Filed Dec. 16, 1944 mlmmuum Patented Nov. 22, 1949 CFFICE COMPENSATOR FOR AIRCRAFT CABLE CONTROLS Oscar Schwimmer, Los Angeles, Calif.

Application December 16, 1944, Serial No. 568,549

13 Claims. 1

This invention relates to tensioning devices for cables and the like, and pertains more specifically to spring-actuated apparatus having especial utility as a means for maintaining the normal rigged tension of control cables of aircraft, being adapted to compensate for variations in cable length or in distance between cable terminals, incident to temperature change, or stretch of the cables due to excessive whipping or the application of extreme working tensions to the cables at a time when manual readjustment is not practicable, e. g., while the aircraft is in flight.

It is common practice to utilize cables as part of the actuating mechanism of the directional apparatus of aircraft, i. e., rudder, ailerons, elevators, and the like. In order to assure immediate and effective response to the pilots manipulation of the cockpit controls, it is essential that the tension of all such Ecables be critically preadjusted and maintained. Turnbuckles are normally employed in control cable assemblies for this purpose, and under ordinary circumstances may be relied upon as a convenient means for manually taking up slack due to elongation produced by normal work tensions.

However, cable tensions may be affected during flight as a consequence of changes in temperature which not only result in contraction and elongation of the cables themselves, but causes the entire metal fuselage to shrink or expand as well, and to a greater extent than the cables, producing a slack in the latter, which seriously impairs the sensitivity of the controls. To overcome this dimculty, a resilient element of sufficient strength to sustain extreme loads but normally only partially extended when the cables are adjusted to mean tensions are incorporated. However, the interposition of a spring in the control cable assembly, in the absence of auxiliary locking means, precludes positive and faithful transmission of control impulses, due to the tendency of the resilient element to absorb the load, as, for example, in aircraft when a sudden change in direction of flight at high speed is necessitated.

Accordingly, in the art prior to my invention, numerous spring compensators have been evolved to compensate for variations in cable length or terminal distance, incorporating means for momentarily locking the unit against further expansion and contraction when any sudden tension is applied to the control cables, as might result from an abrupt change in direction of ight. It will be appreciated, however, that great stress may be gradually laid upon one or the other of the dual cables of a control, as, for example, upon theelevators -of an aircraft when pulling out of a power dive. In such case, there being no sudden application of tension upon the cable of the control assembly, the device remains as a resilient element in the cable assembly, absorbing the initial tensioning of the cables incident to manipulation of the cockpit controls, and preventing sensitive response of the ship.

It is a general object of the present invention to obviate the dificulties aforementioned by the provision of a compensator, embodying a resilient element having means for connection to each of a pair of cables, preadjusted to mean uniform tension and adapted to maintain the static load thus imposed under working conditions by compensating for variations in eiiective length of the cables resulting from temperature change, the resilient element being rendered instantaneously inoperative incident to the application of greater tension to one or the other of the cables, while maintaining the previous adjustment of the compensator.

More speciiically, an object hereof is: the provision of a device adapted for engagement with each of a pair of cables of the character commonly employed as a part of the actuating mechanism for aircraft flight control units, operable to maintain a uniform regulated tension on both cables when the flight control unit and its cockpit controls are in mean positions unaffected by external influences, in combination with means to positively lock the device against further compensatory adjustment, in response to any disparity between the tensions of the respective cables with which the device is utilized whether such variation in tension results from manipulation of the cockpit controls or from aerodynamic factors, ice or -other iniluences acting directly upon the flight control unit with whichthe cables are connected.

Another object is to provide a balancing unit adapted to equalize tension upon each of a pair of cables, the tension being predetermined by a resilient element, and to maintain, substantially, that adjustment during the application of greater tension to one or the other of the cables as during a change in direction of flight.

Still another object is to provide a compensator of the character above alluded to which is entirely mechanical in operation, obviating the production of internal pressures common in hy- `draulic units, and, being unaffected by external my invention, such, for example, as simplicity ofdesign, durability, facility of inspection and lubrication, ease of replacement of worn parts, and

light-weight construction, will be apparent to those of skill in the art upon an examination of -v y the following description, read in the light of the accompanying drawings, in which;

Fig. 1 is a view, principally in elevation, o f one embodiment of my invention, with the parts` thereof extended and the spring relatively relaxed;

Fig. 2 is an elevation of the lower part of the device, taken at right angles to the View of Fig, l; Fig. 3 is a sectional View on lines 3-3 of Fig. 2, depicting the helix by which the locking means is actuated;

Fig. 4 is an elevation of. one of the two movable locking plates;

Fig. 5 is an elevation of one of the stationary locking plates carried by the frame in the assembly;Y

Fig. 6 is an elevation of one end of the helix forming a part of the locking means;

Fig. '7 is a view in elevation, showing the opposite end of the heli-x Fig. 8 is a side elevation of the yoke member.

Referring to. the Vdrawings lin detail, the numerals of which indicate similar parts throughout the several views, I Il designates anat head having holes through opposite sides for the extension` of screws, bolts, or the like, b y which the device may be secured to a suitable mounting adjacent the cables to be serviced. One end .of .a helical spring I-I is accommodatedby an annular groove i2 in one side .of the head, the walls of the groove serv-ing to reinforcev the spring against lateral displacement. f Spring II is normally held under compression by a cupshaped retainer I3v threaded on the end-of a. tubular tie rod I 4. The rod extends through spring II and head I0, terminating in threaded engagement with a T-bar i5 held by the .expansive urge of spring I I against the head. Opposite sides of head IB are cut away as at .IS for the attachment of the .ends of four elongated gibs Il, two of which are secured to each side of the head spaced relation by screws or other suitable means. are rmly held in parallel rigid relationship `by a base plate I8 to which theropposite end of each of gibs Il' is mounted. Opposed edges of each pair of gibs are formed with Vv-shaped .guide grooves I9 for a purpose later referred to. indicates a perforated lug integral Awith and pro.-

jectingfrom one edge .of base plate AIt for the extension of suitable means of attachment by which the unit may be mounted more firmly .in its desired location. As lightweight construction ,is of pri-me importance in all aircraft equipment, gibs I'I ma-y be provided, as illustrated, with a plurality of lightening holes 2 I.

interposed `between head I0 and each pair of Gibs AI 1 Vshaft 2t and slides 25.

be described is adapted to reciprocate in response to variations in tension applied to the control cables with which the apparatus is associated. A pair of rectangular slides 25, having their longitudinal edges formed to correspond with the V-shaped grooves 9 in gibs Il, are mounted between each pair of gibs, respectively, for reciprocation relative to head Ii l A hollow lock-control shaft 261s formed with reduced ends 21 and 21a, respectively, which extend through the slides. @ne end Zia, of shaft 2t is square in cross section, and is received by a square opening in one of slides 25 so as to resist relative rotary motion between The intermediate portion of the shaft is formed with integral helical projections 28 which are received in correspondinglyshaped grooves 29 in the bore of a yoke member 30whereby the complementary helices of shaft 26 and yoke St function to compel the latter to shift laterally in response to the slightest rotary motion imparted to the yoke. Hubs v3I projecting` co-axially from opposite sides of yoke 3o provide mountings, respectively, for a pair of movable locking plates 32. Each of plates 32 is formed with a plurality of parallel serrations 33 forming teeth identical in size and spacing tothose of plates 22, andwith the teeth of which they are adapted to engage in opei'ation.` 'lhe yoke assembly is secured to T-bar i5 byfa'pin 35 DIO- 30Y jecting through oneof slides 25 and., extending freely through narrow slot extensions 3d in. the stationary plates 22, and through holes in movable plates 32 and T-bar I5, is threaded into the opposite. slide.

Yoke. 30 is formed with a pair Vof perforated tensioning cables through which the compensa?.

4. tory adjustment is effected.

The operation of .my invention as applied to the tensioning of aircraft cables is briefly de.-` scribed` as follows By preliminary tensioning, the yokey assembly is shifted to approximately the middle of its normal range-of movement between .retainer I3 through the tie rod I4. Thereafter, 50

any uniform expansion or .contraction of the cables or fuselage Vresulting in a reduction or extension of the distance between the terminals of the cables, or in the lengths .of the latter, in

. responseto temperature change, is automatically compensated by the actionof the spring I I shift.-

strictingthe yoke 4in its movement in response to I Variations in uniform .tension applied to both cables. V

However, the operation by the pilot yof the cockpit `control leversinot shown) for changing the direction of flightimposes a greater strain on one or the other of the control cables. .This

greater tension on one of thecontrol cables is transmitted through the tensioning cable associated therewith to the corresponding side of yoke 30, causing the latter to tilt slightly. In response to this slight rotary motion of the yoke, the complementary helical formations 2B and 29 on the shaft and in the bore of the yoke, respectively, cooperate to shift the yoke laterally, urging the teeth of the movable plate 32 located at the side of the yoke, toward which latter is shifted into locking engagement with the teeth of the adjacent stationary locking plate 22. Due to the small size of the teeth of the respective locking plates and .close tolerances of all parts of the locking assembly,only a very slight tilting movement of the yoke is required to engage the lock. Accordingly, with the yoke thus held against movement longitudinally of the device, spring Il is rendered inoperative, and the directional apparatus is immediately responsive to the slightest re-adjustment of the cockpit controls. It will be noted that the very slight relief of tension applied to one or the other of the control cables incident to tilting of yoke 3E) in effecting engagement of the lock is taken up in the other control cable, due to the increase in tension, to a corresponding degree, by the movement of the other ear 36 of the yoke in the opposite direction.

Accordingly, it will be observed that either one or the other pair of locking plates may be engaged whenever the uniformity of the tension applied to the respective control cables is interrupted, and that the lock will be actuated regardless of whether the variation in tension of the respective cables is the result of manipulation of the cockpit controls or from the action of aerodynamic forces on the surfaces of the directional control mechanism itself. Immediately, as a balanced load is restored to the control cables, e. g., when normal flight is resumed, yoke member 30 will again assume a position perpendicular to the longitudinal axis of the compensator, whereupon the pressure of the yoke upon locking plates 32 is relieved, permitting spring il to again function to effect a readjustment and to maintain both cables under the predetermined rigged tension.

While the illustrated embodiment is designed particularly for use in aircraft, and the above description contemplates, principally, such use, it will be apparent to those of skill in the art that the unit is by no means limited to this application; that numerous changes in size, design, shape and proportion of the various parts may be made to adapt it for utility in other apparatus of analogous or dissimilar nature-all without departing from the scope of my invention as defined in the appended claims.

What I claim and desire to secure by Letters Patent is:

1. In a device of the character described, a frame, a member movable relative to said frame, and locking means associated with said lastnamed member to resist said movement between said member and frame, comprising a helical element actuated in response to tension applied to said member and frame.

2. In a device of the character described, a frame, a member movable in said frame having a pair of cable-engaging elements lying in a common plane, parallel to the plane of the cables to be tensioned, a resilient element to urge said member toward one end of its range of movement, and a locking device for preventing the movement between said member and frame afore- 6 mentioned operable in response to motion of said member in a direction transverse to the plane in which said elements are disposed, relative to the frame.

3. In a device of the character described for tensioning cables, a frame, a member movable in said frame in a direction coinciding with the plane of the cables to be tensioned, and locking means operable to lock said member and frame against relative movement in said direction in response to movement of the member in said frame in a direction transverse to the plane of said cables.

4. In a device of the character described, a

' frame, a slide operable in said frame, a yoke having a helical bore, a helically formed shaft projecting through the bore of said yoke and secured to said slide, the helical formations of said bore and shaft being effective to shift said yoke laterally incident to pivotal movement of said yoke on said shaft, and locking means interposed between said yoke and said frame actuated in response to lateral motion of said yoke.

5. In a device of the character described, a frame, a yoke assembly, means to guide said yoke assembly in reciprocable movement relative to the frame, said yoke assembly comprising a yoke and means to support said yoke for pivotal movement relative to said frame, means to lock said yoke assembly to prevent said reciprocable movement, and means to shift said yoke laterally in a direction substantially parallel to its pivotal axis in response to pivotal movement of the latter to actuate said locking means.

6. In a device of the character described, a frame, a yoke assembly, means Vcarried by said frame to guide said yoke assembly in reciprocable movement relative to the frame, said yoke assembly comprising slides engaged by said means, a shaft, and a yoke pivoted on said shaft, a stationary serrated locking plate carried by said frame, and a movable serrated locking plate carried by said yokeassembly adjacent said stationary plate, said shaft and yoke having complementary helical formations operable to shift said yoke laterally in response to pivoting of the latter relative to said frame to engage said plates.

7. In a device of the character described, a frame, a pin movable in said frame in a direction transverse to the axis of the pin, a yoke pivoted on said pin and movable with said pin relative to said frame, and locking means to resist movement of said pin in Said frame actuated in response to movement of said yoke in a direction substantially parallel to the axis of said pin.

8. In a device of the character described, a frame, a pin movable in said frame in a direction transverse to the axis of the pin, a yoke pivoted on said pin and movable with said pin relative to said frame, and locking means comprising a pair of serrated plates secured to said frame and yoke, respectively, and engageable With one another to lock said pin and frame against movement transverse to the axis of said pin, actuated in response to movement of said yoke in a lateral direction axially of said pin.

9. In a device of the character described, a pair of members relatively movable in directions transverse to one another, and locking means comprising a pair of serrated plates secured to said members and movable therewith respectively, the serrations of said plates being engageable to lock said members against relative movement in one direction in response to movement of said mem- 7 hers relative i0 prie ansthsrifi the Qthsi iiiiiistion.

1Q- in a devise of the siisrffistsr iisssiibsi, a frame, a yoke assembly, means to guide said yoke assembly in reciprocable movement relative to the frame said volss assembly soiiprisiiia a risks and, means to pivotall'y support said yoke for pivotal movement relative to said framefineans to lock said yoke assembly relative to said frame to prevent said reciprocable movement, and means 9perable in response to the pivoting of the yoke t0 shift said yoke laterally in a direction substantially parallel to "the axis of said pivoting meansto actuate said locking means:

11. In a devise 0i the diameter described ist ierisisriiiis sables, a frame@ roster-having ssblef engaging ends. pivotsd and resinrsisabis within saidframe, means to iirsesaid roster tnwardroiis end of said frame, locking-means, interposed between said.Y frame and rockerV to, lockzthe same against reciprocable movement, and means carfA red by said rocker movable laterally in a direc-- tion transverse to the plane of the cables to be tensioned to actuate said locking means.

12. In a device of the character described, a frame, a pin movable in said frame in a direction transverse to the axis of the pin, a yoke pivoted onl said pin and movable with said pin relative to said iframe shift said vaise laterally in a direction substantially parallel to the axis of said nin, and locking means tp resist movement of; said pin m said frame actuated in Iresponse to said iateraiiiifivsiiisiii .0f said yoke.

13. a device m"A the character described, a frame, a pin movable in said frame in al direction transverse tg the axis of the pin, a yoke pivoted on said pin and. movable with said pin relative to sailiframe, and locking means comprising a pair of lserraired plates/y secured to said frame and valsa issesiiveivi sind siigaasabls with ons auf other to lock said pin and frame against movemerit; transverse toaxis of said pin, actuated in response to pivotal movement ofA said yoke.

' OSCAR SCHWIMMER.

REFERENCES CITED The following` references are of record in the file of this patent:

STATES PA'I'ENTS Number Name Date 586,587 Bezel: July 20, 1897 1,219;342. Meyers -f Mar. 13, 1916 2,289,106 Sturgessl Apr. 21, 19,42 2,298,611 Bruderlin Oct. 13, 1942 2,327,021 Cushman Aug. 17, 1943 

